2001×（1/8-1/2009）+8×（1/2000-1/2009）-2009×(1/8+1/2001)
=(2001-2009)/8-(2001+8)/2009+8/2000-2009/2001
=-1-1-1+8/2000-8/2001
=-3+1/500250
=-2又500249/500250